In one example, a device for coding video data includes a video coder configured to code, for a bitstream, information representative of which of a plurality of video coding dimensions are enabled for the bitstream, and code values for each of the enabled video coding dimensions, without coding values for the video coding dimensions that are not enabled, in a network abstraction layer (NAL) unit header of a NAL unit comprising video data coded according to the values for each of the enabled video coding dimensions. In this manner, NAL unit headers may have variable lengths, while still providing information for scalable dimensions to which the NAL units correspond.